Some molds need multiple parts so the cast object isn't trapped inside. Designing the parts requires sculpting a temporary clay dam around the object to contain the plaster while it transforms from liquid to solid. Once the plaster has hardened the clay is removed and recycled into another temporary functional sculpture / micro architectural space. I really enjoy this part of the process and thought I'd share:
This is my favorite so far. Coddle form dome spaceship.
The next step complete: plaster poured (frosted, actually).
The resulting part.
This makes me think of a science fiction book I read years ago. Space traveling beings that built everything with mud. Organic architecture. Mixed with Noah's Ark, mid construction.